The Equal Area Series (197690) is one of several large-scale works by Walter De Maria in Dia’s collection. Beginning in the mid-1970s, Dia commissioned and now maintains for visitors some of De Maria’s most significant permanent site-specific installations, including The Lightning Field (1977), on a remote desert plateau near Quemado, New Mexico, and The Broken Kilometer (1979) and The New York Earth Room (1977), both in downtown Manhattan, New York…